Hello. Thanks for asking from HCM. I can understand your concern. Your son had post traumatic black eye. As concussion has been ruled out, you should not worry. You can carefully watch for alarming signs of head injury like vomiting, loss of consciousness, memory disturbances, bleed through nose/ear/throat. Theses signs and symptoms usually manifest with in few hours of serious head injury. Your son is having headache, nausea, cold and chills. Cold can cause nausea and headache. As the injury is old, swelling is gone, more chances are that symptoms are due to cold. Headache occurs because of fever, nasal blockade due to sinusitis. Nausea may be due to drug side effects taking for cold or fever. So you should take opinion of physician for cold. At home, you can give him steam for 5 minutes every 4 hourly, hot beverages like ginger tea or coffee, use warm clothes to protect from cold and avoid cold food or liquids. The doctor may advise you some blood tests like blood count, haemoglobin and prescribe medicines like paracetamol for fever, antiallergics and nasal decongestants, antibiotics like co-amoxyclav therapy for cold. There is no need to worry. Thanks. Hope it will help you. Take care.